194 Transactions of the Society. 



flagella in active motion. The time the organism continues in 

 this state varies very greatly, a fair average being an hour and a 

 half. At length it very rapidly rounds up and takes on an oval 

 form, and then swims off with intense rapidity, the body remaining 

 rigid. This free-swimming phase usually lasts for an hour or so, 

 when it suddenly comes to a standstill, again becomes amoeboid, 

 the flagella being cast off, and the form then resembles the amoeba 

 as found in the pockets. Multiplication is by binary fission, the 

 nucleus appearing to go through a simple karyokinetic phase. No 

 syngamy has at any time been observed during continuous observa- 

 tion of the species. 



EXCY STATION. 



It was thought desirable to conduct some experiments with the 

 cysts obtained from these pyorrhoea cases. In the amoeba studied 

 by Cropper and Drew, an enzyme which was of a peptic nature 

 was shown to be necessary for excystation, and the amoebae could be 

 caused to excyst in a weak pepsin-hydrochloric acid mixture. In 

 the present amoeba pepsin was never able to cause excystation, and 

 did not appear to have any action on the cyst wall. Horse, human, 

 and raljbit sera were likewise found to be without any definite action 

 on such cysts. Cysts, however, freed from living bacteria, and 

 washed with sterile saline, to remove as many of the accompany- 

 ing dead bacteria as possible, when placed on the special live 

 slide, were found to excyst with the products formed in broth 

 by the following bacteria : Bacillus pyocyaneiis, B. coli, B. Jluorescens 

 non-liquefaciens, Staphylococcus aureus, Streptococcus pyogenes, and 

 B. tctani. 



The organisms were grown in broth for a week at 37° C. and 

 then filtered through a Chamberland F. filter. Similar results 

 were obtained if the sterile broth products were mixed with the 

 jelly used for growing the amcebse, the mixing being done at 

 45° C. to avoid destruction of the enzymes. Bacteria-free cultures 

 were thus obtained, and, if supplied with dead bacteria and fresh 

 serum, could be maintained for some weeks on the special jellies. 

 This particular amoeba is fairly tolerant of acid, but very rapidly 

 rounds up and encysts if placed in pepsin-hydrochloric acid, • 2 p.c. 

 each. It is highly probable, therefore, that the amoeba encysts in 

 the stomach. 



It will be observed that from a consideration of its life-cycle, 

 and the type of nucleus, that this amoeba undoubtedly belongs to 



EXPLANATION OF PLATE XVII. 

 The various stages in the life-cycle of Amoeha buccalis (semi-diagrammatic). 



